Reversible thermosensitive coloring composition and reversible thermosensitive recording medium using the same
A reversible thermosensitive coloring composition is provided, which contains (a) an electron-donating coloring compound; and (b) an electron-accepting compound, which is an aromatic carboxylic acid compound comprising at least one hydrocarbon group, which induces color formation in the electron-donating coloring compound. The reversible thermosensitive coloring composition reversibly assumes a color-developed state or a decolorized state, in response to at least one of (1) the temperature thereof when heated and (2) the cooling rate of the reversible thermosensitive coloring composition when cooled after the heating thereof. A reversible thermosensitive recording medium using the coloring composition is also provided.
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Claims
1. A reversible thermosensitive recording medium comprising:
- a support; and
- a thermosensitive recording layer formed thereon, comprising a reversible thermosensitive coloring composition which comprises (a) an electron-donating compound, and (b) an electron-accepting compound, which is an aromatic carboxylic acid compound comprising at least one aliphatic hydrocarbon main chain moiety having at least 11 non-aromatic carbon atoms, which induces color formation in said electron-donating coloring compound, said composition reversibly assuming a color-developed state or a decolorized state in response to at least one of (1) the temperature of said reversible thermosensitive coloring composition when heated and (2) the cooling rate of said reversible thermosensitive coloring composition when cooled after the heating thereof.
2. The reversible thermosensitive recording medium as claimed in claim 1, wherein said aromatic carboxylic acid compound is represented by formula (I): ##STR317## wherein r is an integer of 1 or 2; X is a bivalent group comprising at least one moiety selected from the group consisting of --NH--, --O--, --S--, --CO--, --CS-- and --SO.sub.2 --; R.sup.0 is hydroxyl group, an alkyl group having 1 to 6 carbon atoms, an alkoxyl group having 1 to 6 carbon atoms, a halogen atom, or a hydrogen atom; and R.sup.1 is an unsubstituted or substituted hydrocarbon group comprising an aliphatic hydrocarbon main chain moiety having at least 11 non-aromatic carbon atoms.
3. The reversible thermosensitive recording medium as claimed in claim 2, wherein said aliphatic hydrocarbon main chain moiety further comprises an aromatic ring.
4. The reversible thermosensitive recording medium as claimed in claim 2, wherein said hydrocarbon group represented by R.sup.1 has a substituent selected from the group consisting of hydroxyl group, a halogen atom and an alkoxyl group.
5. The reversible thermosensitive recording medium as claimed in claim 1, wherein said aromatic carboxylic acid compound is represented by formula (II): ##STR318## wherein r is an integer of 1 or 2; t is an integer of 0 or 1; Y is a bivalent group comprising at least one moiety selected from the group consisting of --NH--, --S--, --CO--, --CS-- and --SO.sub.2; R.sup.0 is hydroxyl group, an alkyl group having 1 to 6 carbon atoms, an alkoxyl group having 1 to 6 carbon atoms, a halogen atom, or a hydrogen atom; and R.sup.1 is an unsubstituted or substituted hydrocarbon group comprising an aliphatic hydrocarbon main chain moiety having at least non-aromatic carbon atoms.
6. The reversible thermosensitive recording medium as claimed in claim 5, wherein said aliphatic hydrocarbon main chain moiety further comprises an aromatic ring.
7. The reversible thermosensitive recording medium as claimed in claim 5, wherein said hydrocarbon group represented by R.sup.1 has a substituent selected from the group consisting of hydroxyl group, a halogen atom and an alkoxyl group.
8. The reversible thermosensitive recording medium as claimed in claim 1, wherein said aromatic carboxylic acid compound is represented by formula (III): ##STR319## wherein r is an integer of 1 or 2; t is an integer of 0 or 1; Z and W are each independently a bivalent hetero-atom-containing group; R.sup.0 is hydroxyl group, an alkyl group having 1 to 6 carbon atoms, an alkoxyl group having 1 to 6 carbon atoms, a halogen atom, or a hydrogen atom; and R.sup.1, R.sup.2 and R.sup.3 are each independently an unsubstituted or substituted hydrocarbon group.
9. The reversible thermosensitive recording medium as claimed in claim 8, wherein said unsubstituted or substituted hydrocarbon group represented by R.sup.1, R.sup.2 or R.sup.3 comprises an aliphatic hydrocarbon main chain moiety having at least 11 non-aromatic carbon atoms.
10. The reversible thermosensitive recording medium as claimed in claim 9, wherein said aliphatic hydrocarbon main chain moiety further comprises an aromatic ring.
11. The reversible thermosensitive recording medium as claimed in claim 8, wherein said hydrocarbon group represented by R.sup.1, R.sup.2 or R.sup.3 has a substituent selected from the group consisting of hydroxyl group, a halogen atom and an alkoxyl group.
12. The reversible thermosensitive recording medium as claimed in claim 8, wherein said bivalent hetero-atom-containing group represented by Z or W is selected from the group consisting of --NH--, --O--, --S--, --CO--, --CS-- and --SO.sub.2 --.
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Type: Grant
Filed: Sep 20, 1996
Date of Patent: Aug 3, 1999
Assignee: Ricoh Company, Ltd. (Tokyo)
Inventors: Masafumi Torii (Shizouka), Hiromi Furuya (Shizouka-ken), Masaru Shimada (Shizuoka-ken), Kyoji Tsutsui (Mishima)
Primary Examiner: Lynette F. Smith
Assistant Examiner: Datquan Lee
Law Firm: Oblon, Spivak, McClelland, Maier & Neustadt, P.C.
Application Number: 8/710,718
International Classification: B41M 520; B41M 524;
